This is a fairly entry level question, but one I feel the need to get answers to.

I have a ground fault in my electrical installation that gives me a measured voltage of 230v AC between ground and L1 or L2 and about 3v between ground and L3. The ground fault source is outside of my house (neighbours or something) so i cant do much about that in the short term.

Does having this pose any threat to esd sensitive equipment if worked on with an ESD mat connected to ground? Would i be better off leaving the ESD mat disconnected from ground an leaving just me and the mat connected?

 

The way you describe L1, L2 and L3 you are describing what would be a 3 Phase Delta configuration with a ground fault. What are you expecting to see? A three phase delta 230 Volt configuration will float above but not be referenced to ground. So what exactly is the entry power supposed to be? Again, reference to L1, L2 and L3 implies 3 phase power entry.

Your ESD station should be configured according to specification meaning any mot or wrist straps are grounded through an appropriate resistance.

Ron

 

It's most common to see an ESD setup that is connected to a grounded outlet. However, the BEST way is to connect it to a grounding rod driven approximately 8 feet into the ground. If you can provide yourself with a grounded rod or other grounded source such as a cold water copper or cast iron pipe (not plastic, plastic doesn't conduct) you can accomplish the same thing.

You ask about grounding yourself to the project. ESD events are when a difference in voltage potential exist. If you're sitting at (oh, lets say) 20,000 volts static and (oh, lets say) your computer is sitting at 2,000 volts, there exists a difference of 18,000 static volts. Upon approaching or touching the computer you can discharge that 18,000 volts into your mother board, thus, blowing it out. When you ground directly to your project you and your project remain at the same potential. When both you and the project are at the same potential there is very little chance you can hurt anything. Keep in mind if you're sitting on a fabric chair, movement can generate static charges. If you have a plastic floor protector mat and you're wearing socks, simply dragging your feet across the mat can generate 10's of thousands of volts very quickly. Especially in dry air conditions (not humid).

Best - grounding rod. If not available, cold water pipe. If not available, at least grounding to the chassis of your project, you get relatively protected results. Not the best, but better than nothing. OR better than you being grounded and your project not.

 

That gave me some good points with regards to do's and dont's about ESD sensitive work. Unfortunately I cannot use a separate grounding rod as I still live in my parents' house. As for water pipes, they are bonded to the same earth as the rest of the house, so not any different from the electrical outlet. I'll stick to grounding the mat with the included 1 Megaohm cable into the electrical outlet and connect myself and the equipment to the mat.

Thanks for the replies, both of you.

 

I guess that there is a need in professional electrician

 

yeah, friend, you're totally right! When the conversation goes to the questions about electricity it's really worth calling a professional electrician. For example, when I decided to change the wiring in my mother's house, I've connected everything according to the logic but not the real computing... And you know what? When I turned on the electricity, the circuit breaker often went off and there the lights started humming and sometimes flickering... To be honest, I've never seen my mom so frightened... As a result, I called an electrician from the company about which you can find more if you enter site, I explained him the situation, and that "poor" man had to fix what I'd done... I was so ashamed... As a result, that electrician connected everything correctly pre-calculated voltage and current flow (simply I've observed that he calculated something according to the physical formula. But the most pleasant thing is that that electrician didn't take extra payment for the remade work